U.S. patent number 5,879,402 [Application Number 08/651,403] was granted by the patent office on 1999-03-09 for method and apparatus for implanting an acetabular cup.
This patent grant is currently assigned to Howmedica International Inc.. Invention is credited to Peter Lawes, Robin S. M. Ling.
United States Patent |
5,879,402 |
Lawes , et al. |
March 9, 1999 |
**Please see images for:
( Certificate of Correction ) ** |
Method and apparatus for implanting an acetabular cup
Abstract
A method of implanting an acetabular cup which includes the step
of preparing an acetabular socket to receive a cup, placing cement
in the acetabular socket before or after locating a tube in line
with the acetabular socket and inserting the acetabular cup through
the tube and into the socket.
Inventors: |
Lawes; Peter (Maidenhead,
GB2), Ling; Robin S. M. (South Devon,
GB2) |
Assignee: |
Howmedica International Inc.
(Shannon, IE)
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Family
ID: |
10744365 |
Appl.
No.: |
08/651,403 |
Filed: |
May 22, 1996 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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329353 |
Oct 26, 1994 |
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Foreign Application Priority Data
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Oct 29, 1993 [GB] |
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9322383 |
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Current U.S.
Class: |
128/898; 606/91;
623/908 |
Current CPC
Class: |
A61B
17/8808 (20130101); A61B 17/8802 (20130101); A61B
17/8816 (20130101); A61B 17/7098 (20130101); A61F
2/4609 (20130101); A61F 2210/0004 (20130101); A61F
2002/30062 (20130101); Y10S 623/908 (20130101); A61F
2002/3429 (20130101); A61F 2002/4631 (20130101) |
Current International
Class: |
A61F
2/46 (20060101); A61F 2/02 (20060101); A61F
2/32 (20060101); A61F 2/34 (20060101); A61F
002/34 () |
Field of
Search: |
;623/16,18,22,23
;606/91,92,93,94 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0073604A1 |
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Mar 1983 |
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EP |
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WO 8504567 |
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Oct 1985 |
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WO |
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Primary Examiner: Isabella; David
Attorney, Agent or Firm: Richardson; Peter C. Akers;
Lawrence C. Augustin; Raymond W.
Parent Case Text
This is a continuation of application Ser. No. 08/329,353, filed on
Oct. 26, 1994 now abandoned.
Claims
We claim:
1. A method of implanting an acetabular cup prosthesis in an
acetabular socket comprising the steps of:
preparing an acetabular socket to receive an acetabular cup, said
cup having an outer diameter at a trailing end thereof;
placing cement in said socket;
locating a tube in line with said socket said tube having an inner
diameter;
inserting an acetabular cup through the tube and into said socket
with said trailing end facing outward; and
pressurizing the bone cement with a means for sealing said inner
diameter of said tube, said means located adjacent said trailing
end of said cup.
2. The method of implanting an acetabular cup as claimed in claim 1
further including the step of locating a flexible skirt assembly
around a rim of said socket, said tube extending from said flexible
skirt, and inserting the acetabular cup through the tube and into
the socket.
3. The method of implanting an acetabular cup as claimed in claim 2
further including the step of securing the flexible skirt around
the rim of the socket to prevent the escape of cement and allowing
the cement to be pressurized.
4. The method of implanting an acetabular cup as claimed in claim 3
further including the step of removing the tube and leaving the
flexible skirt secured to the rim after the cup has been
located.
5. The method of implanting an acetabular cup as claimed in claim 3
which includes removing the skirt after location of the cup and
setting of the cement.
6. The method of implanting an acetabular cup as claimed in claim 3
which includes the step of holding the flexible skirt in place by
attachment elements.
7. The method of implanting an acetabular cup as claimed in claim 2
further including the step of pressuring the cement and controlling
the pressure of the pressurized cement by allowing the cement the
escape from the socket and through a controlled orifice in the
skirt.
8. The method of implanting an acetabular cup as claimed in claim 2
in which the tube is integral with the flexible skirt.
9. The method of implanting an acetabular cup as claimed in claim 2
in which the flexible skirt is removably connected to the tube.
10. The method of implanting an acetabular cup as claimed in claim
2 in which said flexible skirt is made from a synthetic plastics
material.
11. The method of implanting an acetabular cup as claimed in claim
10 in which said flexible skirt is made from polyethylene,
polypropylene, or polyurethane.
12. The method of implanting an acetabular cup as claimed in claim
2 in which said flexible skirt is made from a resorbable
material.
13. The method of implanting an acetabular cup as claimed in claim
12 in which said flexible skirt is made from polyglycolic acid or
polylactic acid.
14. The method of implanting an acetabular cup as claimed in claim
2 which includes the steps of placing the cup inside the tube and
locating the cup within the tube in relation to a locating element
formed on the tube.
15. The method of implanting an acetabular cup as claimed in claim
14 in which said locating element in said locating step is a
projecting collar formed on the inside of the tube, which collar is
dimensioned to engage a flange on said cup with which it is to be
used.
16. The method of implanting an acetabular cup as claimed in claim
15 which includes the step of using an inserter in the form of a
piston insertable within said tube to push cement down the
tube.
17. The method of implanting an acetabular cup as claimed in claim
16 which includes using said inserter for pushing said cement to
push the cup down the tube.
18. A method of implanting an acetabular cup prosthesis in an
acetabular socket comprising the steps of:
preparing an acetabular socket to receive an acetabular cup;
placing cement in said socket;
locating a tube in line with said socket;
locating a flexible skirt assembly around the rim of said socket,
said tube extending from said flexible skirt;
inserting the acetabular cup having a gap in a flange thereon
through the tube and into said socket; and
placing the cup inside the tube and locating the cup within the
tube orienting said gap in said flange in relation to a locating
element in the form of an abutment on the inner diameter of the
tube.
19. The method of implanting an acetabular cup as claimed in claim
18 in which said locating element is a projecting collar formed on
the inside of the tube, which collar is dimensioned to engage a
flange on a cup with which it is to be used.
20. The method of implanting an acetabular cup as claimed in claim
19 which includes the step of using an inserter in the form of a
piston to push cement down the tube.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method and instrumentation for
implanting an acetabular cup which is to be held in place by
polymethyl-methacrylate (PMMA) bone cement.
2. Description of the Prior Art
It is known, for example, to provide a flexible flange around the
rim of an acetabular cup to pressurize the cement, but this only
occurs as the cup approaches its final position in the acetabulum.
The flexible flange touches the acetabular margin tending to
occlude cement flow.
Another device for pressurizing cement is known as the Exeter
Acetabular Pressurizer. In this arrangement a water filled seal
mounted on the end of a handle is used after the acetabulum has
been filled with cement, but before the cup is introduced, the seal
covers the acetabulum and the surgeon pushes on the handle thereby
forcing the doughy cement in the holes, ridges and trabeculae of
the acetabulum. When the instrument is removed and the pressure is
released, blood flow can squeeze between the cement and the
bone.
It is also known to provide cup positioning instruments with long
pointers (vertical, horizontal and at right angles to the patient's
center line of body symmetry) to enable the surgeon to control cup
orientation reasonably well provided the pelvis does not move.
Linear positioning of the cup is determined by eye in a
medio-lateral and anterio-posterior sense. If the natural
acetabulum is well formed, an eyeball judgment can be acceptable,
but many acetabulae are deformed or eroded, in which case eyeball
judgment can be confused.
A further method is to use what are usually referred to as
acetabular spacers. These can be lugs or PMMA spacer (see for
example, U.S. Pat. Nos. 4,883,490 and 4,955,325) fixed to the
outside of the acetabular cup or can be press studs pushed into the
bone base of the natural acetabulum. These prevent the cup from
being pushed too deeply into the acetabular socket and can control
medio-lateral and anterio-posterior positioning. However, they
force some degree of centralization of the cup. If the surgeon
chooses to place the cup eccentrically to make use of a particular
area of solid bone support, acetabular spacers may not permit such
a placement.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method and
apparatus for overcoming some of the difficulties referred to
above, to allow pressurization of the cement so that good holding
is obtained and to provide a method of operation which will ensure
accurate location of the cup in the socket.
According to the present invention a method of implanting an
acetabular cup includes preparing an acetabular socket to receive
the cup, placing bone cement in the socket before or after locating
a loading tube in line with the socket and inserting the acetabular
cup through the tube and into the socket by pushing it down the
tube with an inserter to a predetermined position therein defined
by a stop element acting on the inserter or attachment thereto.
Where the cup is provided with a flanged rim, the stop element can
be arranged within the bore of the tube and the flange rim and the
stop element can be constructed to allow the cup to pass the stop
element but engage the inserter. Another method may include using a
tube and an inserter having a stop element which engage an abutment
on the tube located at a position spaced away from the end of the
tube which is adjacent the socket. If desired, the position of the
stop element can be adjusted prior to use.
The method may also include locating a flexible skirt assembly
around the rim of the socket with the tube extending from the
flexible skirt, and then inserting the acetabular cup through the
tube and into the socket.
With these arrangements, it is possible to either fill the
acetabulum with doughy cement and then reposition the skirt and
tube assembly or the tube on the bone using markers to ensure that
a previously chosen position and orientation are reestablished.
Alternatively, the cement can be injected, for example by a cement
gun, through the tube. The surgeon can then push the cup into the
cement with the inserter to create a pressure and ensure that the
cement fills all the openings in the socket. If the flexible skirt
assembly is used it can be secured around the rim of the socket
preventing the escape of cement and allowing it to be pressurized.
The flexible skirt can be held in place by means of screws, pins
and/or staples, or finger pressure alone.
The method also includes allowing some of the pressurized cement to
escape from the socket and through a controlled orifice in the
skirt. With this arrangement, the tube can be integral with the
flexible skirt or it can be removably connected. Preferably, the
flexible skirt is made From a synthetic plastics material and if it
is to be left in place, could be polyethylene, polypropylene,
polyurethane, or even a resorbable material for example,
polyglycolic acid, or polylactic acid.
In order to locate the cup, the surgeon can control the release of
cement through the orifice in the skirt, and he can push the cup
with the inserter thereby feeling the desired level of cement
pressure. If he is not able to reach the desired predetermined
position when the stop elements are activated, he can release the
pressure on the cement, allowing a little more cement to escape
while the cup progresses further down the inside of the tube. An
expandable tube can be used with a system for adjusting its
diameter.
An advantage of the invention is that no spacers are required which
may cause discontinuities in the cement mantle. The arrangement
also enables the surgeon to accurately locate the position and
attitude of the cup. An apparatus can also be included for
positioning and orienting the tube or the tube and skirt on the
bone into which the cup is to be implanted.
The invention also includes apparatus for use in the method set
forth above which comprises a loading tube adapted for alignment
with an acetabular socket, an inserter adapted to fit into the tube
and stop elements which can act on the inserter or attachment
thereto to limit movement of the inserter down the tube to a
predetermined position therein. The stop element can be provided on
part of the bore of the tube and act on an inner end of the
inserter. This construction is particularly applicable when a
flanged socket is used, the socket being provided with a gap in the
flange.
In an alternative construction stop elements can be provided on the
inserter which engage an abutment on said tube located at a
position spaced away from the end of the tube which is intended to
be adjacent the acetabular socket when in use. This construction
can be used with sockets having a flange or a plain upper rim.
These and other objects and advantages of the present invention
will become apparent from the following description of the
accompanying drawings, which disclose several embodiments of the
invention. It is to be understood that the drawings are to be used
for the purposes of illustration only and not as a definition of
the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings, wherein similar reference characters denote
similar elements throughout the several views:
FIG. 1 is a diagrammatic cross-sectional view of one example of the
apparatus showing the method of operation;
FIG. 2 is a diagrammatic side view of another form of the apparatus
which would be supplied as a series of designs with a wedge or
sloping orientation to accommodate deformed acetabular socket
rims;
FIGS. 3, 4 and 5 show how a step can be machined around the rim of
the acetabulum showing how the apparatus can be used if the bony
rim is eroded;
FIG. 6 shows in diagram form how an orientation guide can be
provided;
FIGS. 7, 8 and 9 show three steps in performing the method and
using the apparatus when using a trial cup;
FIGS. 10 and 11 are views of alternate embodiments of the present
invention; and
FIGS. 12 and 12A are diagrammatic side views of apparatus similar
to that shown in FIG. 11, but without the use of a skirt.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to the figures, there s shown a general form of the
apparatus generally denoted as 100, an acetabular socket being
indicated by reference numeral 1 into which an acetabular cup 2 is
to be fitted.
In order to fit the cup into the socket 1, in which it is to be
held by bone cement in this embodiment, a flexible skirt assembly 3
is utilized. This skirt assembly 3 is made as an integral unit from
a synthetic plastics material, for example polyethylene,
polypropylene, polyurethane, or even a resorbable material, for
example polyglycolic acid, or polylactic acid. The assembly
comprises a flexible skirt 4 which is shown with corrugations 5.
the skirt has a central opening 6 and is provided with a loading
tube 7, the inner bore of which is substantially the same diameter
as the opening 6. The lower end of the loading tube is formed with
an inwardly projecting abutment 8. The acetabular cup 2 has an
annular flange 9 having a gap 14 which is dimensioned to allow the
abutment 8 to pass through it.
To implant the cup 2, the acetabular socket 1 is first prepared in
the usual way for example, by reaming. The flexible skirt assembly
3 is now placed in the position shown in full lines in the drawing
and the skirt 4 is bent and fixed to the bone around the acetabular
opening by pins, screws or staples indicated b reference numeral
10. The deformed position of the skirt when in its secured position
is indicated in broken lines. If desired, the skirt 4 can be
preformed to the required shape. The relative positioning on to the
acetabular bone can be controlled by positioning guides, with or
without fixing.
Prior to fastening it is position, however, the position and
orientation of the tube 7 are determined during the early
preparatory stages of the operation and once this has been
determined, the skirt 4 can be trimmed if necessary and fastened in
position. It will be seen that on the right-hand side of FIG. 1 the
width of the skirt 4 has been trimmed down to assist in
location.
The prepared acetabulum is now filled with cement through the
piston tube 7, the cement being pushed into place by a manually
operated inserter in the form of a piston 11. The piston is removed
when the cement is partially set and in an adequately doughy stage.
The cup 2 is immediately inserted down the tube 7 using the same or
an alternate inserter and thus the cement is pressurized from the
moment the cup touches it. The gap 14 in the cup flange 9 is
aligned with the abutment 8. In the arrangement shown, the piston
11 is used to push the cup into place the piston descending until a
peripheral portion of the edge of its front face 61 engages
abutment 8 thereby preventing the surgeon from pushing the cup in
too far and thus locating it at a predetermined position.
As will be seen from the figures, no spacers are required in the
cement mantle which now surrounds the cup and is indicated by
reference numeral 12.
A cement flow release arrangement is provided by the provision of
an orifice 13 in the skirt 4. The hole in the skirt is occluded,
for example by the surgeon's thumb, to thus allow the pressure to
build up and then allow excess cement to escape. With the cup 2 in
place and the cement fully cured the tube is cut away and the
remainder of the skirt left implanted. Alternatively, the tube and
skirt can be removed in their entirety.
In the arrangement described above, the piston tube is integral
with the skirt 4 but if desired it could be made as a separate
removable item. The use of the skirt 4 also enables the position
and orientation of the cup to be determined prior to actual
insertion, and allows the surgeon to place it precisely where he
wants it in the acetabular socket.
It will, of course, be necessary to provide skirts in a choice of
internal shapes and sizes to suit the chosen cup shape and size.
The loading tube can also be provided in a similar choice of
diameters, but an expandable tube could be set to the required
diameter and fixed with a circumferential strap, an inserter, for
example, in the form of a piston of appropriate dimensions being
employed.
FIG. 11 shows another method and construction in which the cup can
be accurately located in the socket and the same reference numerals
are used to indicate similar parts to those shown in FIG. 1. With
this construction, however, stop means are provided in the form of
an adjustable disc 70 carried on a piston rod 71 of the piston 11.
The disc 70 is held by a grub screw 72 passing through the disc and
bearing against the piston rod 71. The screw 72 can be released to
allow adjustment of the disc 70 on the rod 71.
As will be seen from FIG. 11, a cup 2 with a full projecting
annular flange 9 is used but the position of the cup in the socket
12 is located by adjustment of the disc 17 which acts to limit the
movement of the piston 11. As with the construction shown in FIG.
1, the tube 7 and the flange 3 can be removed completely after the
cement has cured or the tube can be cut away and the flange 3 left
in place. If desired, an adjustable loading tube as shown in FIG. 2
can be used.
FIG. 2 shows a construction of combined skirt 4 and tube 7 which
can be used for deformed/eroded acetabular rims. The tubes and
skirts can be supplied as a series of designs with a wedge or slope
orientation to accommodate different angles of deformity, the slope
angle in FIG. 2 is indicated by reference numeral "A".
As can be seen in FIG. 2, in this construction the length of the
lower end of the inner bore wall 15 varies about the diameter to
provide the angled effect shown. A piston 11 and stop element are
used as shown in FIG. 11, but if desired the stop element of FIG. 1
could be utilized, a suitable abutment being provided on the inner
bore wall.
The series of designs could, of course, also be provided in
different sizes as well as in wedge/ramp angles. This construction
can also be provided by arranging for the skirt 4 and lower part of
the tube wall 15 to be deformable so that the desired shape and
wedge/ramp angle is formed by the operating surgeon. The natural
bony rim of the acetabulum is not a uniplanar circular feature and
if desired, the surgeon can machine a step around the rim to
receive a sealing feature or the like.
FIGS. 3 and 4 show how a trepanning cutter 20 is used to machine
the rim depth to provide a step 21 inside the natural bony rim. The
natural depression in the rim of the acetabulum is indicated by
reference numeral 22. FIG. 5 shows how a skirt 23 can be used which
provides an inwardly directed ledge 24 when placed on the step 21.
The skirt extends upwardly and then outwardly and a removable
loading tube 25 is placed in position on it. As will be seen from
FIG. 5, the deformable skirt 23 is large enough to extend around
and cover the natural dip 22 and prevent loss of cement when the
piston 11 is operated. Once again, the stop element can be as shown
in FIG. 1 or FIG. 11, and an adjustable tube can be used if
desired.
The tube 25 can be arranged so that it is a relative push fit into
the walls of the step 21 where they are covered by the upstanding
portion of the skirt 23. It will be appreciated that a fixed tube
25 fixed to the skirts 4 could be used if desired.
In present surgical techniques, positioning and orientating an
acetabular cup is sometimes achieved using a cup
introducer/inserter with two alignment pointers, one of which
points at 90.degree. across the center line (axis of symmetry) of
the patient and the other points vertically. This controls only
orientation. Position and depth of insertion are chosen by the
surgeon by eye.
In the construction shown in FIG. 6, the same reference numerals
are used to indicate parts as shown in FIGS. 1 and 2 and an
orientation guide 30 is provided which has a carrier 31 which
surrounds the tube 7 and a long handle 32. The handle 32 carries
adjustable alignment pointers 33, 34. The flexible skirt 4 can be
steered by the handheld alignment and orientation guide 30 which is
provided with a handle grip 35. The skirt is flexible enough to
cope with deformed bony rims around the natural acetabulum and the
alignment and orientation guide keeps everything in position and
maintains the skirt 4 tight against the bone.
FIGS. 6, 7, 8 and 9 show an alternate method of employing the
apparatus. An important task in this type of operation is to define
the desired position and orientation of the cup. This is usually
done by putting a trial or dummy implant in place. Theoretically,
it could be determined before the operation using X-rays.
When using the present invention, it is necessary to place the tube
and skirt such that the cup will eventually be positioned and
tilted as required. The tube and skirt might be placed over a
trial/dummy cup fixed and then the trial/dummy removed.
Alternatively, the surgeon might remove the trial/dummy first and
immediately fit the tube and skirt on the basis that his eyeball
judgment of position and orientation is good enough.
FIG. 7 shows a prepared acetabulum 1 into which a trial acetabular
cup 40 has been fitted. At this stage the surgeon chooses the
position of center and orientation.
FIG. 8 shows how the surgeon can now fit the flexible skirt 4
around the trial cup 40 and the trial cup can then be removed, as
indicated by arrow 41, without disturbing the skirt 4. After the
trial cup 40 has been removed, leaving the flange in place, there
is space for the loading tube (with or without an internally
projecting abutment 8 according to the apparatus used) to be
assembled to the skirt 4, for example as shown in FIG. 9, and for
the implant equivalent to the trial cup 40 but necessarily smaller
in size to be put in position.
FIG. 9 shows one way of carrying out the procedure referred to
above by using a separable loading tube 42 which is pushed into
place within the opening in the skirt 4, the flexible construction
of the skirt enabling the tube to be pushed into place with a
tight, sliding fit. If desired, a depth stop abutment ring 43 can
be provided to control the insertion of the tube into the skirt, as
shown in FIG. 9. Due to the deformities of the natural acetabulum,
this abutment ring 43 will not necessarily contact the skirt around
the full periphery. If desired, the abutment ring 43 could be a
tight sliding fit on the tube 42 so that it could be moved under
pressure on the tube to provide a further adjustable depth
stop.
FIG. 10 shows the piston 11 at its lower most position allowed by
abutment 8. A portion of the gap 14 in flange 9 which allows the
cup flange to pass through abutment 8 is also shown.
The lower end of the tube can have an abutment to provide stop
means, or an arrangement as shown in FIG. 1 car be used. The tube
can be cut away once the cup has been inserted or can be simply
dismantled from the cup and skirt.
In FIG. 12 another method of implanting the cup 2 is shown and the
same reference numerals as those used in FIG. 11 are again used to
indicate similar parts. With this method no skirt 4 is used. The
surgeon first prepares the socket 12 in the usual way and then
employs a trepanning cutter in the manner shown in FIG. 3 and 4 to
provide a step 21 inside the natural bony rim. The outer wall 80 of
the step 21 is dimensioned so that the outer wall 81 of the tube 7
is a push fit onto the step 21.
In order to implant the cup the surgeon first places the tube 7 in
position on the step 21 and the cement is then pushed into place by
manual operation of the piston 11. The piston is removed when the
cement is partially set and in an adequately doughy stage. The cup
is now immediately inserted down the tube 7 and the cement is
pressurized from the moment the cup touches it. The cup is pushed
further downwards into the socket 12 to the desired position
provided by the adjustable disc 17.
A tube and piston construction as shown in FIG. 1 can alternatively
be used in a similar manner. An adjustable tube 7 can be used, for
example, of the kind shown in FIG. 1. Once again, it will be seen
from the drawing that no spacers are required in the cement mantle
12.
The essence of the present invention is to provide continuous
cement pressurization during the fitting of the socket and accurate
location of the cup in the acetabular socket.
It will be appreciated that variations of the various embodiments
described can be made by incorporating the different details and
the method may vary by incorporating the different methods
described together.
* * * * *